[TLS] draft-ietf-tls-oob-pubkey: The Open Issue

[Hannes Tschofenig <[e-mail]>]

Hi all, 

draft-ietf-tls-oob-pubkey specifies a new TLS certificate type for exchanging raw public keys in Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) for use with out-of-band public key validation.

Here is the latest draft: 
http://tools.ietf.org/html/draft-ietf-tls-oob-pubkey-03

I would be great to get your feedback on an open issue that concerns the semantic of the exchange. I believe there are three use cases we would like to support with this work. Below, I provide high level message exchanges to explain those: 

I) Server uses Raw Public Keys (client authentication happens at some other layer)
(the DANE use case)

client_hello, 
raw-public-key-indicator="Server, when you send me your raw public key? I support this out-of-band key validation using DANE." ->

                          <-  server_hello,
                              raw-public-key="OK. The certificate structure below contains my raw public key.",
                              certificate, // with raw public key inside 
                              server_key_exchange,
                              server_hello_done

client_key_exchange,
change_cipher_spec,
finished                  ->

                          <- change_cipher_spec,
                             finished

Application Data        <------->     Application Data


II) Client and Server use Raw Public Keys
(the smart object use case - CORE working group)

client_hello, 
raw-public-key="Server, please send me your raw public key and I will then send you mine. Are you OK processing my raw public key for client authentication?" ->

                          <-  server_hello,
                              raw-public-key="Below you find my raw public key and please send me your raw public key for client 
							   authentication",
                              certificate, // raw public key
                              server_key_exchange,
                              certificate_request,
                              server_hello_done

certificate, // with client's raw public key
client_key_exchange,
certificate_verify,
change_cipher_spec,
finished                  ->

                          <- change_cipher_spec,
                             finished

Application Data        <------->     Application Data


II) Hybrid Scenario
(the OAuth Holder-of-the-Key Use case)

client_hello, 
raw-public-key="I would like to use my raw public key for client authentication with OAuth. I also process X.509 for server-side authentication." ->

                          <-  server_hello,
                              raw-public-key="Please send me your raw public key. I use X.509 for server-side authentication",
                              certificate,  // with X.509 cert.
                              server_key_exchange,
                              certificate_request,
                              server_hello_done

certificate, // with client's raw public key
client_key_exchange,
certificate_verify,
change_cipher_spec,
finished                  ->

                          <- change_cipher_spec,
                             finished

Application Data        <------->     Application Data
--------

QUESTION: Are these all the message exchanges we need? Are there some problems with the exchanges? 

Ciao
Hannes